Light sources such as light-emitting diodes (LEDs) are an attractive alternative to incandescent and fluorescent light bulbs for illumination devices due to their higher efficiency, smaller form factor, longer lifetime, and enhanced mechanical robustness. However, both packaged LEDs and bare-die LEDs generally exhibit Lambertian luminous intensity distributions, which may not be useful for lighting applications. Thus, LED-based lighting systems typically require one or more additional or external collimators, mixing chambers, and/or optical elements to produce a desired luminous intensity profile that is useful for lighting, such as a batwing, a narrow batwing, a spot or a flood distribution, or to be useful for applications such as cove lighting or wall washing. Higher light intensities and larger light sources typically require larger and/or more complex optical systems. For example, a lighting system having several high-power LEDs may require a relatively large mixing chamber as well as a relatively complicated optical system to reduce glare to acceptable levels and to achieve a specific light-distribution pattern.
In some cases it is desirable for a luminaire or lighting system to be able to produce different light-output patterns, for example, a bat-wing distribution with different beam widths, or a relatively collimated beam or a tilted or asymmetric beam. In conventional lighting systems, a new optical system is generally required for each different light-distribution pattern. This results in additional manufacturing cost as well as requiring the stocking of multiple different optical systems for each luminaire.
Conventional LED systems also typically require some form of heat-sinking or thermal management that is difficult to incorporate in relatively small and enclosed spaces. Additionally, such systems may require extra ventilation, for example, passive ventilation or active ventilation (e.g., fans), to prevent deleterious heat buildup. These constraints typically lead to undesirably large, thick, and potentially complicated and expensive lighting systems.
Furthermore, from a design perspective, it is often desirable to have an illumination source be able to conform to a curved surface, or to itself have one or more curves. It is also desirable for such structures to be relatively thin, so that they do not add bulk or detract from the surrounding architecture. In some applications, it is desirable for the lighting equipment to be relatively inconspicuous or to essentially disappear. While simple curved structures may be approximated by a large number of rigid circuit boards, this approach is very expensive, requiring a custom solution for each application and complicated and time-consuming installation. The large number of separate boards and interconnects between boards may also lead to reliability problems. As the shape to be covered or approximated becomes more complex, this approach also increases in cost and complexity. A further disadvantage of such an approach is that it may be difficult to make small-volume, inconspicuous, or relatively invisible lighting systems, because of the need for relatively large thermal-management systems.
In view of the foregoing, a need exists for systems and techniques enabling the low-cost design and manufacture of compact reliable lighting systems having low glare with the ability to produce different light-distribution patterns.